The subject matter is heating and cooling and more particularly a predetermined variable recovery of waste heat from a coolant fluid for positive use in combination with a coordinated dissipation of unrecovered heat.
An environment where the system of this invention might be used, for example, is in an industrial plant having heat engines or other equipment of the type generating heat and requiring a coolant fluid. The heat carried away from such machinery by a coolant fluid has heretofore generally been dumped by means of the most convenient sink. In addition, the prior art teaches the utilization of reclaimed heat in an air intake duct through which fresh outdoor air is supplied to the interior of a building. In such instances, the prior art employs apparatus for selectively utilizing equipment generated energy to heat fresh outdoor air during winter months, for example, and wasting the equipment generated energy to atmosphere during warmer months. In other words, the prior art teaches the use of two independent sub-systems--one being used to heat indoor air and the other being used to waste heat to the outdoors. However, a significant drawback encountered in employing two such independent systems resides in the fact that the potential advantages offered by both cannot be realized in a coordinated sense since only either the indoor heat recovery system or the outdoor heat dissipation system is used at one time. Due to changing ambient conditions and heat generation rates, it has been found desirable to only recover a certain proportion of heat from a coolant fluid while dissipating a certain proportion thereof to atmosphere.
For example, heat recovery is most efficient when fresh outside air passed over the interior heat exchanger is very cold and, of course, this efficiency decreases as the outside air temperature increases. One of the effects of such decreasing efficiency with respect to outside air temperature is the increased consumption of electrical energy for a fan or blower to pass outside air over the interior heat exchanger so as to recover any given amount of thermal energy. Within the context of the present invention, an exterior wet surface heat exchanger is preferred for dissipation of heat to atmosphere since the latent heat of evaporation associated with the exterior exchanger provides the capacity to dissipate heat at a greater rate than the sensible heat which can be transferred by the interior heat exchanger for a given air flow. Accordingly, as the temperature of the air passed through the interior heat exchanger increases, the marginally increasing cost of electricity for the blower/fan associated therewith per BTU recovered will not be warranted in comparison to the lesser amount of electrical energy which would be consumed by the blower/fan associated with the more efficient exterior wet surface heat exchanger to dissipate the same quantity of heat from the liquid coolant.
When not employing a coordinated interior and exterior heat exchange system, other disadvantages may be encountered. For example, when drawing outside air over the interior heat exchanger for recovery purposes, the liquid coolant may be of a temperature that it must be cooled but may not be of a sufficient temperature to warrant drawing in cold outside air for interior heating purposes. In addition, there would be the further drawback of relatively greater energy consumption by the interior blower/fan if the interior heat exchanger were to be used as opposed to simply dissipating the excess coolant heat to atmosphere by means of the more efficient exterior, wet surface heat exchanger. Also, and in a sense similar to the coolant not having sufficient excess heat to warm up a given flow of air through the interior heat exchanger to a desired temperature level, the temperature of the would be air flow to be passed through the interior heat exchanger may be so low that it can't be brought up to a desired temperature level whereby it would be more efficient to simply dissipate the excess coolant heat to atmosphere.